Copy letter from Robert William Frederick Harrison, to the Clerk of the Worshipful Company of Plumbers, 1 Adelaide Buildings, London Bridge 'Sir, I am directed by the President to acknowledge your invitation, dated the 1st inst. [instant] and your subsequent note of the 8th inst., and to say in reply that he regrets that he will be unable to attend the conference summoned for the 28th inst. Yours faithfully, Robt [Robert] Harrison Asst Sec RS [Assistant Secretary, Royal Society]'. 12 February 1906